Control system for a load hoisting device



Nov. 17, 1959 H. LINDSTROM 2,913,129

CONTROL SYSTEM FOR A LOAD HOISTING DEVICE Filed July 16, 1957 40 2 Power Supply United States Patent CONTROL SYSTEM FOR A LOAD HOISTING DEVICE Henry L. Lindstrom, Amherst Township, Erie County, N.Y., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application July 16, 1957, Serial No. 672,317

Claims. (Cl. 212-21) The present invention relates, in general, to a control system for a load hoisting device, and more particularly to such a control system in which the operator of the hoisting device is required to reset or take some definite affirmative action as a safety measure once a predetermined maximum travel load hoisting position has been reached.

In accordance with the teachings of prior art control systems for similar load hoisting devices, a limit switch has been provided in the path of the load such that if the load is hoisted up to a predetermined maximum upward travel position, the limit switch will open a first set of its contacts to deenergize the hoisting motor and, in addition, will close a second set of its contacts to provide a dynamic braking circuit including a resistance member in the motor armature circuit until the motor operation is stopped. Thereafter, under certain conditions the load may move in a downward direction until the limit switch closed its first set of contacts to again energize the motor and opened the second set of its contacts to open the dynamic braking circuit. The motor may then again lift the load up into said predetermined maximum travel position to cause the limit switch to again deenergize the motor and complete the dynamic braking circuit. 'Thusly, an objectionable cycling or pumping operation would result.

Accordingly, it is an object of the present invention to provide an improved control system for a load hoisting device, which control system is more desirable and safer in operation.

It is another object of the present invention to provide an improved control system for a load hoisting device wherein the operator cannot cycle or pump the load relative to a predetermined maximum load travel position.

It is a further object of the present invention to provide an improved control system for a load hoisting device having an operators control unit and a load carrying movable trolley member, in which a control member, for example, a circuit breaker device is positioned a sufiicient distance away from the operators control unit such that the operator, if he allows the load to be hoisted into a predetermined maximum travel position, must move away from his control unit and operate said control member before he can again move the load with the load hoisting device.

It is a different object of the present invention to provide an improved control system for a load hoisting device in which a reset control member is provided, and should the load be hoisted into a predetermined maximum upward travel position, this reset control member must then be operated before the hoist motor can again be energized.

It is an additional object of the present invention to provide an improved control system for a load hoisting device wherein movement of the load into a predetermined maximum travel position causes the hoist motor to be deenergized and, in addition, a reset control member is provided in a remote and inconvenient position and must be operated before the hoist motor can again be energized.

It is a still further object of the present invention to provide an additional and safety control member for a load hoisting device which cannot be tied down or made inoperative by the hoisting device operator.

These and other objects and advantages of the present invention will become apparent in view of the following description taken in conjunction with the drawings, wherein:

Figure l is a diagrammatic View of a load hoisting device in accordance with the present invention; and

Fig. 2 is a schematic diagram of the load hoisting apparatus in accordance with the present invention.

in Fig. 1 there is shown a load hoisting device including abase member 10 and a trolley member 12 movable along said base member 10 by means of wheels 14 and 16. The base member 10 includes wheels 18 and 20 operative with and movable along supporting rails 22 and 24, respectively. The base member 10 includes an operators cab 26 in which is positioned a drum switch 28, or similar control device, connected through a multiple strand conductor 30 to a suitable control apparatus 32. A plurality of wire conductors 34 are provided on the base member 10, with the control apparatus 32 including suitable connectors operative with said conductors 34 and the trolley member 12 including a connecting arm 36 and suitable sliding connectors operative with the plurality of conductors 34. A hoisting motor 38 is mounted on the trolley member 12 and suitably connected to a hoisting drum 40 as well as known to persons skilled in this art. A connecting line member 42 is wrapped around the drum 40 and is connected to a I suitable hook device 44 for connection to a load 46 to be hoisted.

A magnetic braking device 48 is operative with the motor 38 and hoisting drum 40 for stopping the movement of the latter hoisting drum 40. A limit switch 50 is provided on the trolley member 12 and is operative with a weight member 52 carried by the connecting line 42 such that if the hook 44 is raised above a predetermined maximum travel position, the weight member 52 contacts the arm 59 of the limit switch 50 to deenergize the hoisting motor 38 as will be later described. A manual reset control 56 including a manual control button 58 is provided on the base member 10 and is operative with the control apparatus 32 as will be later described. A suitable power supply 60 may be connected through terminals 62 and 64, or longitudinal conductors, and sliding contactors 63 and 65 mounted on the base member 10 for supplying power to the load hoisting device in accordance with the present invention.

In Fig. 2 there is shown the power supply 60 connected through suitable conductors 66 and 68 to energize and control the hoisting motor 38 including a commutating field winding 70 and a series field winding 72. The drum switch member 28 is shown in Fig, 2 schematically as having five hoisting or upward travel speeds and five lowering or downward travel speeds. The drum switch member 28 includes a first contactor 74 which is closed only in the 01f position to energize through a contactor 75 the control winding 76 of a low voltage master relay MR including a contact 78. Thusly, in the off position of the drum switch 28, the master relay contact 78 is closed whenever power is supplied from the power supply 60 through conductors 66 and 68 to the load hoisting device in accordance with the present invention, as may in actual practice be controlled by additional contacts or? switch members, not shown, but well known to persons skilled in this art. The drum switch 28 further includes contacts 80, 82, 84, 86 and 88, etc. as well known to persons skilled in this particular art. The schematic showing of the drum switch 28 includes five vertical lines representing these five speeds of the hoist position and similarly five vertical lines representing the five speeds of the lowering operation. The illustrated controller segments are operative with the respective contactors 80, 82, 84, 86, 88 and as well known when the drum switch 28 is in the respective positions represented by the vertical lines for the load hoisting operation and the load lowering operation. In other words, when the drum switch 28 is in the first speed position of the load hoist operation, the contactor 80 is connected to the contactor 82 and the contactor 84. The contactor 88 is connected to the contactor 89. With the contactor 80 connected to the contactor 82, the control winding 90 closes the contactor 91 of the relay device 1M in series with the shunt resistance 92 and the series field winding 72 of the motor 38 and the control winding 94 of the brake device 48 shown in Fig. 2.

Since the contactor 84 is connected to the contactor 88 through the controller segment, the control winding 100 for the contact 101 of the relay device 2M is energized to close the latter contact 101 to energize the armature circuit of the motor 38 and the commutating winding 70 through the contacts 102 and 104 of the limit switch 50. Since the contactor 88 of the drum switch 28 is connected to the contactor 89, the control winding 106 for the contact 107 of the relay device 4M is energized to close the latter contact 107 to complete the latter circuit for energizing the motor 38 through the resistors 96 and 98 and from the respective conductors 66 and 68.

The limit switch 50 also includes a contact 108 which is normally open in series with a resistor 110 and an additional contact 112 that is normally open. The latter contact 112 when closed with contact 108 provides a parallel dynamic braking circuit including the series field winding 72 and the resistor member 110 and the motor armature and the commutating winding 70,

The contact 86 of the drum switch 28 is connected to the contact 80 when the drum switch is moved to one of the lowering speeds to thereby energize the control winding 114 for the contact 115 of the relay device 3M, which contact 115 is connected in series with the resistor member 116 and in a suitable control circuit with the resistor members 118 and 120 to be operative with the remainder of the control apparatus 122 shown in Fig. 2 as well known to persons skilled in this art, but not shown in the detailed schematic view. The control of the contacts M, 6M, 7M and 8M to efiectively vary the operation of the hoisting motor 38, is similarly well known to persons skilled in this particular art.

The limit switch 50 is operated by the weight member 52 as shown in Fig. 1 passing beyond a predetermined maximum upward travel position. The limit switch 50 then opens the contact 102 to thereby provide a voltage drop between the conductors 119 and 121, which voltage drop is sensed by the control winding 124 of a relay device B that is operative with the contacts 127 and 75 such that contact 127 is thereby closed, and contact 75 is thereby opened. A rectifier device 126 is placed in series with the first control winding 124 of the relay device B. Closing of the contact 127 energizes the second control winding 128 of the relay device B, which second control winding 128 is operative as a holding winding to hold the relay contact 127 in the closed position and to hold the contact 75 in the open position. It should be noted that the now opened contact 75 deenergizes the control winding 76 of the master relay MR including the contact 78 such that the latter contact 78 opens to deenergize the control apparatus 122 and the drum controller 28 and to thereby stop the operation of the hoisting motor 38. The control handle 29 of the drum switch 28 must be now returned to the oft position to again close the off contactor 74. The reset control switch 56 must now be closed manually as shown in Fig. 2 to energize the control winding 130 for a starting relay SR including contacts 129 and 131 which open when the control winding 130 of the relay SR is .energized. The now open contacts .131

I deenergizes the holding winding 128 of the relay device B holds the limit switch 102 open.

to allow the contact 127 to open and the contact to close. The closing of the contact 75 energizes through the now closed off contact 74, the control winding 76 of the low voltage main relay MR including the contact 78 which now closes. This allows the drum controller 28 to again assume control of the hoisting motor 38 as previously described, and as known to persons skilled in this art.

It should be noted that the rectifier device 126 is poled to conduct current during the load hoisting operation only. When the load is hoisted too high and thereby opens the limit switch 102, the control winding 124 is energized. However, the load is still in its too high position and this When the drum controller is reversed to lower the load, this reverses the polarity of the motor armature current and the rectifier device 126 now prevents the so reversed armature voltage from again energizing the control winding 124. This latter reversed armature voltage, however, energizes the magnetic brake winding 94 to release the brake 48 and allow the weight of the load to lower the load below its too high position and thereby the load recloses limit switch 102 to allow normal operation of the hoisting apparatus.

However, the contact 129 of the starting relay SR including the control winding must again close as accomplished by deenergizing the control winding 130 by opening the manual control reset switch 56. This prevents the human operator from tying down or shortcircuiting the manual control switch 56. When the latter manual control switch 56 is released by the hoist operator to open the circuit through the control winding 130 of the starting'relay SR, the contact 129 again closes to allow the drum switch 28 to control the operation of the hoisting motor 38.

In this respect it should be understood that when the load is lowered below the predetermined maximum up.- ward travel position, the limit switch closes the contacts 104 and 102 and opens the contacts 108 and 112 as shown in Fig. 2 to allow the normal operation of the control apparatus in accordance with the present invention. It should be noted that when the contact 102 closes, the control voltage drop across the contact 102 and sensed by the first control winding 124 of the relay device B disappears such that the control winding 124 is ineffective to open the contactor 75 and ineffective to close the contactor 127 until the limit switch 50 is again triggered by the load being hoisted into the maximum upward travel position as determined by the weight member 52 contacting the arm 54 of the limit switch 50 as shown in Fig. 1.

In accordance with the operation of the present invention, the limit switch 50 is responsive to the load being hoisted into a predetermined maximum upward travel position to open the contact 102 such that a control voltage appears between conductors 119 and 121 to energize the first control winding 124 of the relay B, to close the contact 127 which energizes the second control and holding winding 128 of the relay B and to further open the contact 75 which deenergizes the control winding 76 of the low voltage main relay MR including the contact 78 which now opens. The second control winding 128 of the relay device B is now operative to hold the contact 127 in its closed position and to hold the contact 75 in its now open position. The opening of the contactor 78 of the main relay MR deenergizes the drum controller or switch 28 and stops the operation of the hoisting motor 38.

It is now necessary for the operator to return the control handle 29 of the drum switch 28 to its ofi position to thereby close the ofl? contactor 74. The operator must then leave his cab 26 and move to a position where he can operate the manual control button 58 of the reset switch 56 which closes the reset switch 56 to energize the control winding 130 of the starting relay which opens the contactor 129 and the contactor 131. The opening of the latter contactor 131 deenergizes the control winding 128 of the relay device B which allows the contact 127 to, open and the contact 75 to close. In this regard it should be noted that the voltage across the open contact 102 of the limit switch 50, and between the conductors 119 and 121, disappeared when the control was shut off by the opening of the contact 78 of the main relay such that the first control winding 124 is now no longer operative to close the contact 127 and open the contact 75 of the relay device B.

The subsequent opening of the manual control switch 56 deenergizes the control winding 130 of the starting relay SR to again close the contact 129 and the contact 131. This allows the drum switch 28 to again assume control of the hoisting motor 38 until the load is again moved into the predetermined upward maximum travel position to again operate the limit switch 50 and open the contactor 102, which would again energize the first control winding 124 of the relay device B to open the contact 75.

In Fig. 2 there are shown sliding contacts 150, 152, 154, 156 and 158 which are operative with the conductors 34 of the base member shown in Fig. 1, to allow the portion 160 of the control apparatus shown in Fig. 2 to be mounted on the movable trolley member 12 of Fig. 1.

Although the present invention has been described with a certain degree of particularity, it should be understood that the present disclosure has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the scope and the spirit of the present invention. Further, in this regard, the required overload control relays and certain other control relay devices, including circuit contacts and the like well known to persons skilled in this art, have not been shown in an effort to simplify the present disclosure.

I claim as my invention:

1. In a control system for a load hoisting device including a base member and a trolley member movable along said base member, the combination of a hoisting line adapted for connection to said load, a motor mounted on said trolley member and operative with said line for hoisting the load, motor control apparatus mounted on said base member and operative to control the energization of said motor, a load position responsive device mounted on said trolley member for providing a control signal when the load is hoisted into a predetermined maximum travel position, a first power control device including a first control winding and a first impedance member controlled by said first control winding, with said first impedance member being connected to said motor for controlling the energization of said motor, and with said first control winding being responsive to said control signal for causing said first impedance member to substantially deenergize said motor when said load is in said predetermined position, and a second power control device including a reset control member mounted on one of said trolley and base members, said second power control device further including a second control winding and a second impedance member controlled by said second control winding, said second impedance member being operative with said first impedance member for controlling the energization of said motor, and with said second control winding being operative with said reset control member such that said reset control member must be operated before the second impedance member will allow said motor to be energized.

2. In a control system for a load lifting device including a base member and a trolley member movable along said base member, the combination of a line member adapted for connection to said load, a motor mounted on said trolley and operatively connected to said line member for lifting said load, control apparatus mounted on said base member and operative with said motor for controlling the operation of said motor, a load position responsive device mounted on said trolley member, a power controlling device connected to said motor and operative with said load position responsive device for controlling the operation of said motor, with said load position responsive device being operative to provide a control voltage when said load is in a predetermined maximum travel position, and with said power control device being operated by said control voltage for controlling the load lifting operation of said motor as a function of the position of said load, and a second power controlling device mounted on one of said base and trolley members a predetermined distance away from said control apparatus and operative with said motor for preventing the further control of said motor by the first power controlling device until after said second power controlling device has been operated.

3. In a control system for a load hoisting device including a base member and a trolley member movable along said base member, the combination of a line member adapted for connection to said load, a motor mounted on said trolley member and operative with said line member for hoisting said load, control apparatus mounted on said base member and operatively connected to said motor for controlling the energization of said motor, a load position responsive device mounted on said trolley member and adjacent to said line member and operative to provide a control signal when the load is hoisted into a predetermined maximum travel position, a first power control device responsive to said control signal and operative with said control apparatus for deenergizing said motor when the load is hoisted into said predetermined maximum travel position, and a second power control device including a circuit interrupter mounted on one of said trolley member and base member and operative with said first power control device for controlling the latter first power control device to again energize said motor when it is desired to resume the operation of said motor.

4. In a control system for load hoisting apparatus operative with suitable power supply terminals, said load hoisting apparatus including a base member and a trolley member movable along said base member, the combination of a connection line member adapted to be connected to said load, a motor connected between said terminals and operative with said connection line member for hoisting said load, said motor being mounted on said trolley member to be movable relative to said base member, a first control device having a first control winding and being connected in series with said motor for controlling the energization of said motor, a load position responsive device mounted on said trolley member and operative with said connection line member to provide a control signal when said load is hoisted into a predetermined maximum travel position, a second control device including a second control winding and being connected in series with said first control winding for controlling the energization of said motor, with said second control winding being connected to said load position responsive device for responding to said control signal and for deenergizing said motor when the load is hoisted into said predetermined maximum travel position, and a third control device mounted on one of said trolley member or base member and connected in series with one of said first and second control windings to prevent the reenergization of said motor until after said third control device has been operated.

5. In a control system for a load hoisting device including a base member and a trolley member movable along said base member, the combination of a hoisting line adapted to be connected to said load, a motor mounted on said trolley member and operative with said '7 line for hoisting the load, motor control apparatus mounted on said base member and operative to control the energization of said motor, a load position responsive limit switch device mounted on said trolley member for providing a control signal when the load is hoisted into a predetermined maximum travel position, a first power control relay device including a first control winding and a first switch member controlled by said first control winding, with said first switch member being connected in series with said motor for controlling the energization of said motor, and with said first control winding being responsive to said control signal for causing said first switch member to deenergize said motor when said load is in said predetermined maximum travel position, and a second power control relay device including a second control winding and a second switch member controlled by said second control winding, said second switch member being operative with said first switch member for controlling the energization of said motor, a manually operated switch member mounted on one of said trolley member and base member, and with said second control winding being operative with said manually operated switch member such that said manually operated switch member must be closed before the second switch member will allow said motor to be energized.

References Cited in the file of this patent UNITED STATES PATENTS 941,938 Muller Nov. 30, 1909 2,579,317 Hepperlen et al Dec. 18, 1951 2,724,796 Posselt et al Nov. 22, 1955 

